This is a visual way of checking if your story has enough racial diversity. Start with your main character on the left, pick their skin tone. Then, keep going with characters that have less and less lines/screen time.
Who are the heroes? Who are the villains? Analysis and conclusions are up to you.
(The filled example is my own novel, set in Egypt, and I’m not sure I like the fact that I managed to fit so many white characters in there.)